Fast population and economic growth has largely influenced anthropogenic inputs and riverine export of nitrogen (N) in China, posing risks to human health, water security and ecosystem functioning. Such growth is projected in the coming decades in South Asia and Africa. Climate change adds another level of uncertainty to N pollution in rivers and coastal water. To analyze the impact of these changes, we selected three large river basins of different levels of anthropogenic influence (Indus, Yangtze and Zambezi) and modelled the current (2010) and future (2050) N export to rivers and coastal water. N export was simulated by the MARINA model (Model to Assess River Inputs of Nutrients to seAs), which utilizes outputs from a wide range of models e.g., for crop, land use, nutrients and hydrology. Three scenarios are used for 2050 based on the Shared Socio-economic Pathways (SSPs) and Representative Concentration Pathways (RCPs), representing sustainable (SSP1-RCP2.6), business-as-usual (SSP2-RCP4.5) and high inequality/emission (SSP3-RCP6.0) pathways. Results consistently show the dominant contribution from human activities (agriculture and domestic wastewater) to N export in Yangtze and Indus. In Zambezi, natural sources currently dominate N export (>70%), but substantial increase of human-induced N sources is projected by 2050, especially from domestic wastewater due to the doubling population and limited infrastructure. Although a slight reduction of N export in Yantgze is possible in case of sustainable development (SSP1-RCP2.6), increase of N export by up to 100% is projected in Indus and Zambezi in all scenarios. The impact of climate change is less evident among the scenarios and basins. Nevertheless, intra-basin spatial variability and inter-annual temporal variability of runoff and discharge have a noticeable impact on those of N export. These results suggest that ambitious N management strategies will be needed, especially in Indus and Zambezi for domestic wastewater.